Yogourt Hacking

Yogurt is a product of bacterial fermentation of milk. Here we propose to provide the bacterium Lactobacillus bulgaricus genetic information required in order to produce a certain type of protein called “fluorescent”. The result of the manipulation should be getting a new bacterial strain for the manufacture of yoghurt fluorescent !! :-) Suddenly eating yogurt is much more fun, since it will shine a light in purple :-) !

Isolate bacteria from yogurt

We separate the 2 species of bacteria found in yogurt (j'ai pris un yaourt bulgare), Lactobacillus delbrueckii sp. bulgaricus et Streptococcus thermophilus. Why I spread a dilute solution of yogurt on a Petri dish containing a nutrient medium (by LB, I had it). After 24h of growth at 37 ° C, there are a multitude of circular bacterial colonies. Microbiology is generally accepted that a colony has only one ancestor bacteria as, ie bacteria within a given colony are all the same, we say they are “clones”. Lactobacillus and Streptococcus do not have the same form of cell envelope, Lactobacillus is a bacillus and has a rod-shaped body, Streptococcus cocci and is a spherical body and has a (see pictures). To find it type of bacteria colonies were formed, I take some of this colony and put them on glass slides so they can be easily observed under a microscope.

Results - 2.3.11

I confirmed that all my colonies were formed from rod-shaped bacterium, it is therefore most likely of Lactobacillus bulgaricus. I'll put them in culture to make a stock that I can keep future. It now remains for me to isolate Strepococcus… It is possible that S. thermophillus does not grow on LB, I'll have to find another more suitable culture medium, probably made from milk. I'll let you know !

Edit - 10.3.11

I just found info on how to effectively isolate Lactobacillus and Streptococcus (Vive Google Books !). Instructions →

The fluorescent protein

I will use a low plasmid copy number (order not to destabilize our host beyond measure) gene with the “Green Fluorescent Protein” (GFP). He will speak through a non-regulatable promoter says “constitutive”, to ensure the level of expression of our gene. (I will put the map of plasmid later).

Subsequently arrives…

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Written by webmasterPosted in ProjectsOctober 26, 20115 comments

5 comments

Thomas December 5, 2011

I'm having some trouble understanding the part of the fluorescent protein, could someone explain to me, svp?
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Emma Bernadotte February 22, 2012

Hello,
Thomas, GFP is a fluorescent protein, is in a plasmid that will be inoculated with the bacterial strain by a method known “transformation” (often, heat shock: the plasmid is placed in the presence of the bacterium, is the shock in a pool of hot water at 42 ° C in a conventional protocol; it opens its pores, between the plasmid, then hands it to growth temperature in rich medium story she recovers). The plasmid (Circular DNA) then contains the GFP gene downstream of a promoter. When this promoter is induced, the protein will be expressed, and GFP fluoresces in the green.
By cons, I have a question for the author: do you think there was enough consumable in a yogurt lactobacillus, and the low plasmid copy number has a fairly strong promoter, so that the color may be seen on a yogurt consumable?
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Emilie May 29, 2012

I also have questions for the author : the link for the separation of the two types of bacteria do nothing more leads, I found a few other protocols nevertheless I would like to know which you use ; I also wanted you to know you are available or GFP ; and finally I wonder as Emma Bernadotte on the proportion of each of these bacteria in the final product. Bravo for this original project and attracting!
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Thomas June 10, 2012

Hello Emma, this is a very good question. I do not know the density of bacteria in a dairy product like yogurt. It is clear that the intensity of the fluorescent signal or luminescent (when using the luminescence) is positively correlated with the density. To see when this was put into practice! :)
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caroline December 3, 2012

un rapport de la FAO sur les produits laitiers mentionne 10^8 bacteries par millilitre ( http://www.fao.org/docrep/T4280F/T4280F00.htm )

à rapprocher de l’estimation de densité en bactéries d’une colonie d’Escherichia coli en milieu liquide et riche, en phase stationnaire: 1-2*10^9/ml, mentionné sur le site de bionumbers
(http://bionumbers.hms.harvard.edu/bionumber.aspx?&id=100984&ver=1)

les 2 chiffres ne sont pas loin.

en gros, on peut voir le yaourt comme un milieu de culture pour Lacto. bulg. et Strepto. therm. dans lequel on aurait laissé poussé les bactéries jusqu’à plus faim.

Des nouvelles du projet ?
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